In the prior art, when honing working is to be carried out, a tool with several grindstones attached on its periphery is used, and while the tool is supplied with rotational motion, it is moved in reciprocating motion by a distance corresponding to working area of the work thereby the grinding working is carried out.
One example of such a honing tool is shown in FIG. 1.
The honing tool 61 comprises a hollow mandrel 62, and a plurality of grindstones 66 being provided on the outer circumference of the top end portion 63 of the mandrel 62 and movable in the radial direction. The grindstones 66 are rotated while being pushed to the outside through a bed plate 67 by moving a taper part 65 of a mandrel shaft 64 up and down, and are reciprocated up and down repeatedly by the distance corresponding to the working area thereby the grinding working of a prescribed diameter is carried out.
In the honing working by such a honing tool 61, however, when it is reciprocated up and down repeatedly along a circumferential surface of a hole 81 of a work 80 as shown in FIG. 2, edge of lands 81a is liable to be unsharpened. Moreover, when the lands 81a are different in length, there is a problem that the shorter land 81a is machined more and the finished diameter becomes larger.
If the reciprocating speed is made larger in order to raise the working efficiency, loading or crushing of the grindstone 66 occurs and the efficiency is further decreased.
Therefore some honing tool is provided with two sets of grinding sections in order to raise the working efficiency, and can perform rough machining and finish machining continuously.
FIG. 3 shows a honing tool 71 in such constitution. The honing tool 71 is constituted by a cylindrical body 72, a main machining grinding section 73 being installed at the top end portion of the body 72 and comprising a rough grindstone, and a finish grinding section 74 being installed at the center portion and comprising a finish grindstone. A tapered adjusting rod 75 is fitted to the inside of the main machining grinding section 73 so that the main machining diameter can be adjusted, and a tapered adjusting rod 77 is fitted to the inside of the finish grinding section 74 so that the finish grinding diameter can be adjusted.
The honing tool 71 with the main machining diameter and the finish machining diameter being adjusted is rotated and moved by a distance corresponding to the working area thereby the grinding finishing of the prescribed diameter is carried out.
In such a honing tool 71, however, there is a problem that the honing tool 71 is liable to be rolled laterally with respect to the work thereby the straightness of the hole subjected to the grinding finishing cannot be held. Also when the moving speed of the tool is made larger, there is a problem that loading or crushing of the main machining grindstone 73 and the finish grindstone 74 occurs.